1. Field of the Invention
The present invention relates to polynucleic acid nanostructures and lattices.
2. Description of the Related Art
The control of the structure of matter on the finest possible scale requires the successful design of both stiff intramolecular motifs and robust intermolecular interactions. Previous motifs used to design 2D crystalline arrays have included the double crossover (DX) (Fu et al., 1993; Winfree et al., 1998), triple crossover (TX) (LaBean et al., 2000), the DNA parallelogram (Mao et al., 1999), and the four-by-four structure (Yan et al., 2003). These motifs have been used to produce 2D crystalline arrays lacking symmetry or with twofold symmetry (Seeman, 2003). By contrast, all previous attempts to produce trigonal or hexagonal arrays have met with failure or produced only very tiny structures. Given the inherent rigidity of triangles, the importance of trigonal motifs in nature (Kappraff et al., 1990), it is key to solve this problem. The flexibility of 3-arm junctions was discovered in the first attempt to assemble a hexagonal lattice (Ma et al., 1986). Triangles built from bulged 3-arm junctions (Liu et al., 1994) demonstrated cyclic closure with trimers and above, not just from the hexamers one would have expected (Qi et al., 1996). Triangles whose edges were flanked by coplanar helices derived from DX molecules behaved in a similar fashion (Yang et al., 1998).
Brun et al. (2004), reported experimental evidence of two new complexes, quadruple crossovers and triangles, where atomic force microscopy images (AFM) show that the triangles are capable of hexagonally tiling the plane. However, the triangular units used by Brun et al. to form a hexagonal lattice have single nucleic acid helices for its edge and are not robust, as the AFM image of the lattice formed appears to show that some pentagons and squares are present in the lattice.
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